Torch for powder plasma buildup welding

ABSTRACT

A torch for powder plasma buildup welding capable of readily attaining welding in conformity to any size of a pipe material to be subjected to welding, any configuration thereof and the like. A torch head is replaceably connected to a torch body. The torch body is provided with a gap formation spacer member which is abutted against an inner peripheral surface of the pipe material to keep a distance between an opening of a convergent nozzle of the torch head and the inner peripheral surface of the pipe material substantially constant during buildup welding. Also, the torch body is provided with a deflection restraint spacer member which is abutted against the inner peripheral surface of the pipe material to prevent deflection of the torch body in the pipe material during buildup welding.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a torch for powder plasma buildupwelding, and more particularly to a powder plasma buildup welding torchwherein a torch head is inserted into a pipe material to be subjected tobuildup welding, to thereby carry out the welding on an inner peripheralsurface of the pipe material.

[0002] A typical torch for powder plasma buildup welding which has beenconventionally known or practiced in the art includes a torch head and atorch body for connecting a body of a welding machine such as a powersupply or the like and the torch head to each other therethrough and isadapted to carry out buildup welding on an inner peripheral surface of apipe material. Such a welding equipment is constructed so as to rotatethe pipe material while keeping the torch head and a part of the torchbody inserted into the pipe material and move the torch head in the pipematerial to form a spiral padding on the inner peripheral surface of thepipe material, to thereby attain buildup welding on the pipe material.Such a torch for powder plasma buildup welding is used to carry outbuildup welding on an inner surface of a pipe material for a petroleumreaction pipe, an injection molding cylinder or the like using a weldingmaterial which has corrosion resistance and wear resistance.

[0003] Unfortunately, the conventional powder plasma buildup weldingtorch must be varied in construction depending on dimensions of a pipematerial, a configuration thereof and the like, resulting in handlingthereof being troublesome. In a powder plasma buildup welding torch, thetorch body is formed of a rigid material, to thereby fail to constructthe whole torch in a compact manner, so that transport of the torch istroublesome. This renders repairing of the torch head highly hard whenany failure or trouble occurs in the torch head.

SUMMARY OF THE INVENTION

[0004] The present invention has been made in view of the foregoingdisadvantage of the prior art.

[0005] Accordingly, it is an object of the present invention to providea torch for powder plasma buildup welding which is capable of beingreadily handled irrespective of dimensions of a pipe material, aconfiguration thereof and the like.

[0006] It is another object of the present invention to provide a torchfor powder plasma buildup welding which is capable of facilitatingrepairing of a torch head when it fails or breaks down.

[0007] It is a further object of the present invention to provide atorch for powder plasma buildup welding which is capable of restraininga variation in distance between an opening of a convergent nozzle of atorch head and an inner peripheral surface of a pipe material to besubjected to welding, to thereby form a padding uniform in size thereon.

[0008] It is still another object of the present invention to provide atorch for powder plasma buildup welding which is capable of preventingleaping of a torch body.

[0009] In accordance with the present invention, a torch for powderplasma buildup welding is provided. The torch includes a torch headadapted to be inserted into a pipe material of a continuous length tocarry out buildup welding on an inner peripheral surface of the pipemateriall and a torch body formed into a continuous length and havingthe torch head mounted on a distal end thereof. The torch head isreplaceably connected to the torch body. Such construction permitsbuildup welding to be attained in conformity to any size of a pipematerial to be subjected to welding, any configuration thereof and thelike. Thus, the present invention facilitates application of the torchto welding while eliminating replacement of the whole powder plasmabuildup welding torch required in the prior art. Also, when any failureor trouble occurs in the torch head, the torch head may be readilyrepaired because it is detached from the torch body.

[0010] In general, the torch head includes a convergent nozzle having anopening. In a preferred embodiment of the present invention, eithertorch head or torch body is provided with a gap formation spacer memberwhich is abutted against the inner, peripheral surface of the pipematerial to keep a distance between the opening of the convergent nozzleof the torch head and the inner peripheral surface of the pipe materialsubstantially constant when welding takes place. Such arrangement of thegap formation spacer member in the torch effectively prevents avariation in distance between the opening of the convergent nozzle ofthe torch head and the inner peripheral surface of the pipe materialsubjected to welding due to a weight of the torch head and/or deflectionof the torch body, to thereby ensure formation of a padding of a uniformsize on the inner peripheral surface of the pipe material.

[0011] An increase in length of the torch body tends to cause it to bedeflected in the pipe material during build up welding. In particular,arrangement of the gap formation spacer member causes leaping of thetorch body during rotation of the pipe material depending on abutmentbetween the gap formation spacer member and the inner peripheral surfaceof the pipe material, leading to an increase in deflection of the torchbody. In view of such a disadvantage, the torch body is preferablyprovided with at least one deflection restraint spacer member adapted tobe abutted against the inner peripheral surface of the pipe material soas to prevent deflection of the torch body in the pipe material duringbuildup welding.

[0012] More specifically, in accordance with the present invention, afollowing torch for powder plasma buildup welding is provided. The torchincludes a torch head adapted to be inserted into a pipe material of acontinuous length to carry out buildup welding on an inner peripheralsurface of the pipe material and a torch body formed into a continuouslength and having the torch head mounted on a distal end thereof. Thetorch body includes a connection pipe and a plurality of pipes arrangedin said connection pipe. The plurality of pipes feed cooling water, gasand the like to said torch head, respectively. The plurality of pipesinclude two or more pipes made of an electrically conductive material.One of the two or more pipes constitutes a first conductive portionelectrically connected to one of electric poles of a DC power supply andanother of the two or more pipes constitutes a second conductive portionelectrically connected to the other of said electric poles. The torchhead includes a bar-like electrode, an electrode support made of anelectrically conductive material and arranged for supporting thebar-like electrode, a convergent nozzle made of an electricallyconductive material, a nozzle support made of an electrically conductivematerial and arranged for supporting said convergent nozzle, and ahead-side insulation member arranged between the electrode support andthe nozzle support to electrically insulate the electrode support andnozzle support from each other. The head-side insulation member includesa projection portion projecting beyond the electrode support and nozzlesupport and toward the torch body. The connection pipe of the torch bodyis fixedly provided on an end thereof defined on a side of the torchhead with an insulation flange. The insulation flange is attached with aconnection member. The connection member includes a first connectionmember half and a second connection member half which are arranged so asto be spaced from each other through a cavity defined therebetween andfitted with the projection portion. One of the two or more pipesmentioned above is connected with the first connection member halfthrough the insulating flange. Another of the two or more pipesmentioned above is connected with the second connection member halfthrough the insulating flange. The electrode support is contacted withthe first connection member half. The nozzle support is contacted withthe second connection member half. The torch head is replaceablyconnected to the torch body by means of a plurality of bolts for fixingthe torch head and connection member to each other.

[0013] The torch of the present invention thus constructed facilitatesdetachable connection between the connection member and the torch headby tightening and releasing of the bolts. This permits the torch head tobe replaceably connected to the torch body by means of bolts. Also,connection between the connection member and the torch head leads tojoining between the first connection member half and the electrodesupport, so that a current may be fed from one of electric poles of apower supply (a body of a welding machine) through one of the two ormore pipes constituting a first conductive portion, the first connectionmember half and the electrode support to the bar-like electrode. Also,connection between the connection member and the torch head permits thesecond connection member half and nozzle support to be joined together,so that a current may be fed from the other electric pole of the powersupply (the body of the welding machine) through another of the two ormore pipes constituting a second conductive portion, the secondconnection member half and the nozzle support to the convergent nozzle.

[0014] In this invention, particularly, the head-side insulation memberincludes the projection portion. Thus the positioning between the torchhead and the torch body is easily performed only by fitting theprojection portion into the cavity defined between the first connectionmember half and the second connection member half. The connection membermay be attached with the insulation flange by means of the bolts forfixing the torch head and the connection member to each other. Thispermits the torch head, the connection member and the insulation flangeto be fixed together by means of a small number of bolts.

[0015] In a preferred embodiment of the present invention, the firstconnection member half and the second connection member half each areformed with a plurality of connection member-side bolt insertionthrough-holes. The flange is formed with a plurality of flange-side boltinsertion through-holes aligned with the connection member-side boltinsertion through-holes, respectively. The flange-side bolt insertionthrough-holes each include a large diameter portion receiving thereineach head of the bolts and a small diameter portion receiving thereineach shank of the bolts. The electrode support and the nozzle supporteach are formed with a plurality of threaded holes aligned with theconnection member-side bolt insertion through-holes, respectively. Thetorch head is detachably connected to the torch body by means of boltsthreadedly fitted in the threaded holes of the torch head through theconnection member-side bolt insertion through-holes and flange-side boltinsertion through-holes. Such construction permits the connection memberand torch head to be connected to each other by inserting bolts throughthe connection member-side bolt insertion through-holes and flange-sidebolt insertion through-holes and threadedly fitting the bolts in thethreaded holes of the torch head. Release of the bolts leads toseparation of the connection member and torch head from each other.

[0016] In a preferred embodiment of the present invention, theinsulation flange is formed with flange-side through-holes via which thepipes of the torch body extend and the connection member is formed withfit holes which communicate with the flange-side through-holes and inwhich the pipes are fitted and communication holes which communicatewith the fit holes and are open on-a side of the torch head. The torchhead is formed with in-head passages aligned with the communicationholes. The torch head is connected to the torch body so that thecommunication holes and in-head passages may communicate with each otherat communication portions therebetween. Thus, connection between theconnection member and the torch head leads to communication between thecommunication holes and the in-head passages, so that a current, coolingwater, gas and the like may be fed from the body of the welding machineto the torch head.

[0017] In a preferred embodiment of the present invention, thecommunication portions, at which the communication holes and in-headpassages communicate with each other, each are sealed at a peripheraledge thereof with an O-ring which is arranged at an opening of each ofthe communication holes on a side of the torch head or an opening ofeach of the in-head passages on a side of the connection member. Thispermits the peripheral edge of the communication portion between thecommunication holes and the in-head passages to be effectively sealedwith the O-ring compressed due to tightening of the bolts.

[0018] In a preferred embodiment of the present invention, the torchbody is provided on an end thereof defined on a side of the torch headwith an above-mentioned gap formation spacer member and the torch bodyis provided with an above-mentioned deflection restraint spacer member.

[0019] The gap formation spacer member may be constructed in any desiredmanner. For example, the gap formation spacer member may include anupper head support half and a lower head support half which are combinedwith each other to circumferentially surround the torch body. In thisinstance, the lower head support half may include a lower body portionfor circumferentially surrounding a lower portion of the torch body anda lower projection portion arranged so as to vertically downwardlyproject from the lower body portion, resulting in being abutted againstthe inner peripheral surface of the pipe material. The upper headsupport half may include an upper body portion for circumferentiallysurrounding an upper portion of the torch body and an upper projectionportion arranged so as to project from the upper body portion in aradial direction of the pipe body, resulting in being abutted againstthe inner peripheral surface of the pipe material. The upper projectionportion may have, to the lower projection portion, positionalrelationship which is set to restrain a variation in distance betweenthe torch head and the inner peripheral surface of the pipe materialduring welding.

[0020] In a preferred embodiment of the present invention, the lowerprojection portion includes a projection body threadedly coupled to thelower head support half and a ball member supported in the projectionbody in a rollable manner (hereinafter also referred to as “rollably”)so as to be abutted against the inner peripheral surface of the pipematerial. This permits rotation or rolling of the ball member to reducefriction between the lower projection portion and the inner peripheralsurface of the pipe material, to thereby reduce deflection of the torchbody in the pipe material during buildup welding.

[0021] In a preferred embodiment of the present invention, theinsulation flange is formed into a cylindrical configuration andconstitutes the gap formation spacer member. In this instance, theinsulation flange may be abutted against the inner peripheral surface ofthe pipe material. This eliminates a necessity of providing the gapformation spacer member separately and simplifies a structure of the gapformation spacer member.

[0022] The deflection restraint spacer member may be likewiseconstructed in any desired manner. For example, the deflection restraintspacer member may include an upper body support half and a lower bodysupport half which are combined with each other to circumferentiallysurround the torch body, as well as an abutment member arranged so as tovertically downwardly project from the lower body half, resulting inbeing abutted against the inner peripheral surface of the pipe material.The abutment member may be formed into a plate-like shape and arrangedso as to extend in a longitudinal direction of the pipe material to bewelded. Also, the deflection restraint spacer member may be constitutedby a cylindrical member. The cylindrical member may include a first bodysupport half and a second body support half which are combined with eachother to circumferentially surround the torch body.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] These and other objects and many of the attendant advantages ofthe present invention will be readily appreciated as the same becomesbetter understood by reference to the following detailed descriptionwhen considered in connection with the accompanying drawings; wherein:

[0024]FIG. 1 is a schematic view showing a manner of buildup welding onan inner peripheral surface of a pipe material in accordance to anembodiment of a torch for powder plasma buildup welding according to thepresent invention;

[0025]FIG. 2 is a sectional view showing a structure around a torch headincorporated in the torch for powder plasma buildup welding shown inFIG. 1;

[0026]FIG. 3 is a front elevation view showing a torch head incorporatedin the torch for powder plasma buildup welding of FIG. 1;

[0027]FIG. 4 is a plan view showing a torch head incorporated in thetorch for powder plasma buildup welding of FIG. 1;

[0028]FIG. 5 is a rear view showing a torch head incorporated in thetorch for powder plasma buildup welding of FIG. 1;

[0029]FIG. 6 is a plan view showing a first connection memberincorporated in the torch for powder plasma buildup welding of FIG. 1,which is viewed from a side of a torch body;

[0030]FIG. 7 is a plan view showing a second connection memberincorporated in the torch for powder plasma buildup welding of FIG. 1,which is viewed from a side of a torch body;

[0031]FIG. 8 is a plan view showing an insulation flange incorporated inthe torch for powder plasma buildup welding of FIG. 1, which is viewedfrom a side of a torch body;

[0032]FIG. 9 is a plan view showing a gap formation spacer memberincorporated in the torch for powder plasma buildup welding of FIG. 1;

[0033]FIG. 10 is a side elevation view showing a gap formation spacermember incorporated in the torch for powder plasma buildup welding ofFIG. 1;

[0034]FIG. 11 is a sectional view taken along line XI-XI of FIG. 10;

[0035]FIG. 12 is a side elevation view showing a deflection restraintspacer member incorporated in the torch for powder plasma buildupwelding of FIG. 1;

[0036]FIG. 13 is a bottom view showing a deflection restraint spacermember incorporated in the torch for powder plasma buildup welding ofFIG. 1;

[0037]FIG. 14 is a sectional view taken along line XIV-XIV of FIG. 12:

[0038]FIG. 15 is a plan view showing a structure around a torch headincorporated in another embodiment of a torch for powder plasma buildupwelding according to the present invention;

[0039]FIG. 16 is a partially broken-away side elevation view of thestructure shown in FIG. 15;

[0040]FIG. 17 is a bottom view of the structure shown in FIG. 15;

[0041]FIG. 18 is a plan view showing an insulation flange incorporatedin the torch for powder plasma buildup welding of FIG. 15, which isviewed from a side of a torch body;

[0042]FIG. 19 is a plan view showing a deflection restraint spacermember incorporated in a further embodiment of a torch for powder plasmabuildup welding according to the present invention;

[0043]FIG. 20 is a side elevation view showing a modification of thedeflection restraint spacer member incorporated in a still anotherembodiment of a torch for powder plasma buildup welding according to thepresent invention; and

[0044]FIG. 21 is a sectional view taken along line XXI-XXI of FIG. 20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Now, a torch for powder plasma buildup welding according to thepresent invention will be described with reference to the accompanyingdrawings.

[0046] Referring first to FIG. 1, a manner of buildup welding on aninner peripheral surface of a pipe material carried out in accordancewith an embodiment of a torch for powder plasma buildup weldingaccording to the present invention is illustrated. A torch for powderbuildup welding of the illustrated embodiment which is generallydesignated at reference numeral 1 in FIG. 1 includes a torch head 3, atorch body 5 of a continuous length, a gap formation spacer member 7,and a deflection restraint spacer member 9. The torch head 3 and a partof the torch body 5 are inserted into a pipe material P of a continuouslength to be subjected to buildup welding. Then, the pipe material P isrotated and the torch head 3 is moved in the pipe material P, so thatbuildup welding is carried out on an inner peripheral surface of thepipe material P to form a spiral padding W thereon. In the illustratedembodiment, the pipe material P is formed into an inner diameter of 120mm. The torch body 5, as shown in FIG. 2, includes a connection pipe 11and pipes 13, 15 and 17 arranged in the connection pipe 11 so as to flowa DC current, gas and the like therethrough. This results in a DCcurrent, gas and the like being fed from a body of a welding machine(not shown) to the torch head 3. In the illustrated embodiment, thetorch body 5 is formed into a length of about 5 m. Eight such pipes arearranged so as to feed a DC current, gas and the like therethrough tothe torch head 3. However, only three pipes 13, 15 and 17 are shown inFIG. 2 for the sake of brevity. The connection pipe 11 includes a pipebody 11 a and a small-diameter end portion or an end portion reduced indiameter as compared with the pipe body which is designated at referencecharacter 11 b. The end portion 11 b is arranged on an end of the pipebody 11 a defined on a side of the torch head 3. The pipe body 11 aincludes an outer wall section 11 c and an inner wall section 11 d, tothereby be constructed into a double-wall structure. Between the outerwall section 11 c and the inner wall section 11 d is formed a waterwaylie.

[0047] The torch head 3, as shown in FIGS. 2 to 5, is connected througha first connection member half 21 and a second connection member half 23constituting a connection member 19 described above, and an insulationflange 25 to the connection pipe 11 and includes a bar-like electrode29, an electrode support 31 for supporting the bar-like electrode 29therein, a convergent nozzle 33, a nozzle support 35 for supporting theconvergent nozzle 33 therein and a head-side insulation member 37. Thebar-like electrode 29 is supported in the electrode support 31 through acollet 39 for adjusting centering of the bar-like electrode 29 and acollet holder 41.

[0048] The electrode support 31 is made of an electrically conductivematerial and, as shown in FIGS. 4 and 5, is formed therein with anin-head passage 31 a for feeding cooling water, an in-head passage 31 bfor plasma gas and an in-head passage 31 c for discharging coolingwater. The cooling water feed in-head passage 31 a and cooling waterdischarge in-head passage 31 c are arranged so as to communicate with afirst cooling water feed pipe (not shown) of the torch body 5 and afirst cooling water discharge pipe (not shown) of the torch body througha communication hole 21 d of the first connection member half 21,respectively. This permits cooling water fed from a side of a body of awelding machine through the first cooling water feed pipe and coolingwater feed in-head passage 31 a to the electrode support 31 to bereturned through the cooling water discharge in-head passage 31 c andfirst cooling water discharge pipe to the side of the body of thewelding machine after cooling a peripheral region of an upper portion ofthe bar-like electrode 29. Also, the first cooling water feed pipe inthe torch body 5 connected to the cooling water feed in-head passage 31a constitutes a first conductive portion electrically connected to anegative electric pole of a DC power supply of the body of the weldingmachine. Such construction permits a current to be fed from the DC powersupply through the first cooling water feed pipe (the first conductiveportion), first connection member half 21, electrode support 31, colletholder 41 and collet 39 to the bar-like electrode 29. The plasma gasin-head passage 31 b is arranged so as to communicate at one end thereofwith the plasma pipe 13 of the torch body 5 through the communicationhole 21 d of the first connection member half 21 and communicate at theother end thereof to a through-hole 37 c formed through a centralportion of the head-side insulation member 37 and a through-hole 35 aformed through a central portion of the nozzle support 35. Suchconstruction results in plasma gas fed from the side of the body of thewelding machine through the plasma gas pipe 13 and plasma gas in-headpassage 31 b being fed to a peripheral area at a distal end of thebar-like electrode 29 via the through-holes 37 c and 35 a.

[0049] The convergent nozzle 33 is formed into a cylindrical shape whilebeing gradually reduced in diameter toward a distal end of the bar-likeelectrode 29. Also, the convergent nozzle 33 is supported in the nozzlesupport 35 in a manner to surround the bar-like electrode 29 while beingspaced at a predetermined interval from the bar-like electrode 29.Further, the convergent nozzle 33 has a shield cap 34 arrangedtherearound while being threadedly fitted in the nozzle support 35.

[0050] The nozzle support 35 is made of an electrically conductivematerial as in the electrode support 31 and formed therein with athrough-hole 35 a in a manner to extend through a central portionthereof, in which the bar-like electrode 29 is partially arranged. Also,the nozzle support 35, as shown in FIGS. 4 and 5, is formed therein witha first in-head passage 35 b for a powder, an in-head passage 35 c forshield gas, a second in-head passage 35 d for a powder, an in-headpassage 35 e for feeding cooling water, and an in-head passage 35 f fordischarging cooling water. The first powder in-head passage 35 b andsecond powder in-head passage 35 d are arranged so as to communicate atone end thereof through a communication hole 23 d of the secondconnection member half 23 to first and second powder pipes (not shown)of the torch body 5, respectively. Also, the first and second powderin-head passages 35 b and 35 d communicate at the other end thereof witha powder hole 33 b. This results in a powder which is fed from the bodyside of the welding machine through the powder pipes and in-headpassages 35 b and 35 d being fed through the powder hole 33 b into anarc column discharged between bar-like electrode 29 and the pipematerial P. The shield gas in-head passage 35 c is arranged so as tocommunicate at one end thereof with the shield gas pipe 15 of the torchbody 5 through the communication hole 23 d of the second connectionmember half 23 and at the other end thereof with a shield gas hole 33 c.This permits shield gas fed from the body side of the welding machinethrough the shield gas pipe 15 and shield gas in-head passage 35 c to befed around the arc column. The cooling water feed in-head passage 35 eis arranged so as to communicate the communication hole 23 d of thesecond connection member half 23 to a second cooling water feed pipe(not shown) of the torch body 5 and the cooling water discharge in-headpassage 35 f is arranged so as to communicate through the communicationhole 23 d of the second connection member half 23 to the second coolingwater discharge pipe 17 of the torch body 5, so that cooling water fedfrom the body side of the welding machine through the second coolingwater feed pipe and cooling water feed in-head passage 35 e may bereturned to the body side of the welding machine through the coolingwater discharge in-head passage 35 f and second cooling water dischargepipe 17 after it cools a periphery of a lower portion of the bar-likeelectrode 29. Also, the second cooling water feed pipe of the torch 5connected to the cooling water in-head feed passage 35 e constitutes asecond conductive portion electrically connected to a positive electricpole of the DC power supply on the body side of the welding machine.This permits the convergent nozzle 33 to be fed with a current from thepositive pole through the second cooling water feed pipe (the secondconductive portion), second connection member half 23 and nozzle support35. Thus, a so-called pilot arc is generated between a distal end of thebar-like electrode 29 electrically connected to the negative pole andthe convergent nozzle 33 electrically connected to the positive poleduring welding.

[0051] The head-side insulation member 37 is formed of an insulatingmaterial such as a ceramic material or the like which has a plate-likeconfiguration and arranged between the electrode support 31 and thenozzle support 35 to insulate both from each other. The head-sideinsulation member 37 includes an insulation portion 37 a arrangedbetween the electrode support 31 and the nozzle support 35 and anelongated projection portion 37 b projecting from the insulation portion37 a toward the connection member 19 described below. The insulationportion 37 a is formed therein with the above-described through-hole 37c in a manner to extend through a central portion thereof in a thicknessdirection thereof. The through-hole 37 c has a part of the bar-likeelectrode 29 arranged therein. The insulation portion 37 a, as shown inFIGS. 2 and 4, is formed with bolt insertion through-holes 37 c to 37 iin a manner to extend therethrough in a thickness direction thereof. Ofthe bolt insertion through-holes 37 c to 37 i, the bolt insertionthrough-holes 37 c to 37 e each have a bolt 43 arranged therein so as toextend from the head-side insulation member 37 to the electrode support31. The bolt insertion through-holes 37 c to 37 e each are formed into aconfiguration which prevents a head of the bolt 43 from being contactedwith the nozzle support 35. The head-side insulation member 37 andelectrode support 31 are fixed with respect to each other by extendingthe bolt 43 through each of the bolt insertion through-holes 37 c to 37e and threadedly fitting it in each of threaded holes 31 d formed in theelectrode support 31. Of the bolt insertion through-holes 37 c to 37 i,the bolt insertion through-holes 37 f to 37 i, as shown in FIG. 2, eachhave a bolt 45 arranged therein so as to extend from the head-sideinsulation member 37 to the nozzle support 35. The bolt insertionthrough-holes 37 f to 37 i each are formed into a shape which prevents ahead of the bolt 45 from being contacted with the electrode support 31.Thus, the head-side insulation member 37 and nozzle support 35 are fixedwith respect to each other by inserting the bolt 45 through each of thebolt through-holes 37 f to 37 i and threadedly fitting it in each ofthreaded hole 35 g formed in the nozzle support 35. Also, the electrodesupport 31 is formed at a portion thereof aligned with each of the boltinsertion through-holes 37 f to 37 i with a screwdriver insertion port31 e in a manner to extend therethrough in a thickness direction thereofso that the bolt 45 may be externally secured by means of thescrewdriver.

[0052] The connection member 19 is arranged on an end of the torch body5 defined on a side of the torch head 3 and is constituted by theconnection member half 21 and second connection member half 23 eachformed of an electrically conductive material of a plate-like shape. Thefirst connection member half 21 and second connection member half 23 arearranged so as to be spaced from each other with a gap or cavity beingdefined therebetween. The cavity has the projection portion 37 b of thehead-side insulation member 37 fitted therein. More particularly, thefirst connection member half 21 and second connection member half 23 arearranged in a manner to be insulated from each other while interposingthe projection portion 37 b of the head-side insulation member 37therebetween. The first connection member half 21, as shown in FIGS. 2and 6, is joined to the electrode support 31 and formed with three feedholes 21 a and two connection member-side bolt insertion through-holes21 b in a manner to extend therethrough in a thickness directionthereof. The feed holes 21 a each are formed at a lower portion of acentral section of the first connection member half 21 and include a fithole 21 c positioned on a side of the torch body 5 and a communicationhole 21 d positioned on a side of the torch head 3 and formed into adiameter smaller than the fit hole 21 c. The fit holes 21 c each haveeach of three pipes 13 of the torch body 5 fitted therein and thecommunication holes 21 d each are arranged so as to communicate witheach of the pipes 13 and each of the in-head passages 31 a to 31 c ofthe electrode support 31. The second connection member half 23, as shownin FIGS. 2 and 7, is arranged so as to be joined to the nozzle support35 and formed with six feed holes 23 a and two connection member-sidebolt insertion through-holes 23 b in a manner to extend there through ina thickness direction thereof. The feed holes 23 a each are formed at acentral portion of the second connection member half 23 and include afit hole 23 c positioned on a side of the torch body 5 and acommunication hole 23 d positioned on a side of the torch head 3 andformed into a diameter smaller than the fit hole 23 c. The fit holes 23c each have each of six pipes 15 and 17 of the torch body 5 fittedtherein and the communication holes 23 d each are arranged so as tocommunicate with each of the pipes 15 and 17 and each of the in-headpassages 35 b to 35 f.

[0053] The insulation flange 25, as shown in FIGS. 2 and 8, is formedof, a ceramic material into a plate-like shape and arranged between theconnection member 19 and the torch body 5 or at an end of the torch body5 defined on a side of the torch head 3. FIG. 8 is a plan view of theinsulation flange 25 which is viewed from a side of the torch body 5.The insulation flange 25 is formed with eight flange-side through-holes25 a, three fixing bolt insertion through-holes 25 b and fourflange-side bolt insertion through-holes 25 c so as to extendtherethrough in a thickness direction thereof. The flange-sidethrough-holes 25 a are arranged rather in proximity to a central portionof the insulation flange 25 and each have each of the eight pipes 13, 15and 17 arranged therein so as to extend therethrough. The fixing boltinsertion through-holes 25 b each include a large-diameter portion 25 dpositioned on a side of the torch head 3 and a small-diameter portion 25e positioned on a side of the torch body 5. The insulation flange 25 andtorch body 5 are fixed with respect to each other by inserting a bolt 47through each of the fixing bolt insertion through-holes 25 b into thetorch body 5 and threadedly fitting it in each of threaded holes 11 fformed in the torch body 5. More specifically, the bolts 47 each arethreadedly fitted in each of the threaded holes 11 f while beinginserted through each of the large-diameter portions 25 e and keeping ahead thereof arranged therein. The flange-side bolt insertionthrough-holes 25 c are arranged in a manner to be dispersed on a edge ofthe insulation flange 25 so as to be aligned with the connectionmember-side bolt insertion through-holes 21 b of the connection member19. Also, the flange-side bolt insertion through-holes 25 c each are soarranged that an opening thereof defined won a side of the torch body 5is exposed outside the small-diameter end portion lib of the torch body5. The flange-side bolt insertion through-holes 25 c each include alarge-diameter portion 25 f positioned on a side of the torch body 5 anda small-diameter portion 25 g positioned a side of the torch head 3. Theinsulation flange 25, and the first connection member half 21 andelectrode support-31 are fixed with respect to each other by insertingeach of bolts 49 through two flange-side bolt insertion through-holes 25c positioned on an upper side in FIG. 8 into the first connection memberhalf 21 and electrode support 31 and threadedly fitting it in thethreaded hole 31 f in the electrode support 31. More specifically, thebolt 49 is threadedly fitted in the threaded hole 31 f while extendingthrough the small-diameter portion 25 g and the connection member-sidebolt insertion through-hole 21 b of the first connection member half 21and keeping a head thereof received in the large-diameter portion 25 f.The insulation flange 25, and the second connection member half 23 andnozzle support 35 are fixed with respect to each other by inserting abolt through each of two flange-side bolt insertion through-holes 25 cpositioned on a lower side in FIG. 8 into the second connection memberhalf 23 and nozzle support 35 and threadedly fitting it in a threadedhole (not shown) formed in the electrode support 31. Such arrangementpermits the communication passages 21 d and in-head passages 31 a to 31c to communicate with each other and the communication holes 23 d andin-head passages 35 b to 35 f to communicate with each other, resultingin the connection member 19 and torch head 3 being connected to eachother. Also, release of the bolts 49 leads to separation of theconnection member 19 and torch head 3 from each other. Thus, the bolts49 permit the torch head 3 to be detachably connected to the torch body5. This facilitates replacement of the torch head 3, so that onlyreplacement of the torch head 3 is merely required in order to carry outwelding in conformity to a size of a pipe material, a configurationthereof and the like. Thus, the present invention eliminates replacementof the whole torch for powder plasma buildup welding which is requiredin the prior art, to thereby facilitate handling of the powder plasmabuildup welding torch. Also, it facilitates repairing of the torch headwhen it fails or breaks down, because the torch head is detachablyarranged. Further, the in-head passages 31 a to 31 c and 35 b to 35 feach are provided on a peripheral edge of an opening thereof with anO-ring 51, so that communication regions between the communication holes21 d and 23 d and the in-head passages 31 a to 31 c and 35 b to 35 feach are sealed with the O-ring 51 compressed due to tightening of thebolt 49.

[0054] The gap formation spacer member 7, as shown in FIGS. 1 and 9 to11, includes an upper head support half 53 and a lower head support half55 which are combined with each other to circumferentially surround thetorch body 5. FIGS. 9 and 10 are a plan view of the gap formation spacermember 7 and a side elevation view thereof, respectively, and FIG. 11 isa sectional view taken along line XI-XI of FIG. 10. The upper headsupport half 53 is made of brass and includes an upper body section 57and an upper projection section 59. The upper body section 57 is formedinto a semi-circular shape in section so as to circumferentiallysurround an upper portion of the torch body 5 and includes a groove 57a, two threaded through-holes 57 b, four bolt head arrangement grooves57 c and four bolt insertion through-holes 57 d. The groove 57 a isformed so as to extend in a direction perpendicular to a direction inwhich the torch body 5 extends and formed so as to be upwardly open. Thethreaded through-holes 57 b each are formed through the upper bodysection 57 so as to communicate with a bottom of the groove 57 a. Thebolt insertion through-holes 57 d each are formed so as to communicatewith an interior of each of the bolt head arrangement grooves 57 c andthe lower head support half 55.

[0055] The upper projection section 59 is formed into an elongatedplate-like shape bent at a predetermined angle and includes a supportedportion 59 a, an abutment portion 59 b, and a connection portion 59 cfor connecting the supported portion 59 a and abutment portion 59 b toeach other therethrough. The supported portion 59 a is arranged in thegroove 57 a and has an elongated through-hole 59 d extendingtherethrough in a thickness direction thereof. The upper projectionsection 59 is fixed to the upper body section 57 by means of two boltsthreadedly fitted via the through-hole 59 d in the threadedthrough-holes 57 b of the upper body section 57. The through-hole 59 dis formed into a length larger than a distance between the bolts 61 and61, to thereby be shifted with respect to the bolts 61, to thereby varya position of the upper projection section 59 with respect to the upperbody section 57. The abutment portion 59 b is arranged so as to beabutted at an end thereof against an inner peripheral surface of thepipe material P.

[0056] The lower head support half 55 is made of a material identicalwith that for the upper head support half 53 and includes a lower bodysection 63 and a lower projection section 65. The lower body section 63is formed into a semi-circular shape in section so as tocircumferentially surround a lower portion of the torch body 5 andincludes a lower threaded hole 63 a and four upper threaded holes 63 b.The lower threaded hole 63 a is formed through the lower body section 63so as to be open to a position right below a central portion of thelower body section 63. The upper threaded holes 63 b each are formed soas to be open on a side of the upper head support half 53 and be alignedwith the bolt insertion through-holes 57 d of the upper head supporthalf 53, respectively. The lower head support half 55 is fixed to theupper head support half 53 by means of four bolts 67 threadedly fittedin the upper threaded holes 63 b through the bolt insertionthrough-holes 57 d, respectively.

[0057] The lower projection section 65 includes a projection body 65 aand a ball member 65 b. The projection body 65 a includes a threadedportion 65 c of which an outer periphery is threaded, a tighteningoperation portion 65 d positioned below the threaded portion 65 c, and aball member holding portion 65 e arranged below the tightening operationportion 65 d. The projection body 65 a is fixed to the lower bodysection 63 in a manner to vertically downwardly project from the lowerbody section 63 while keeping the threaded portion 65 c threadedlyfitted in the lower threaded hole 63 a of the lower body section 63. Thetightening operation portion 65 d is formed into a hexagonal shape incross section so that the threaded portion 65 c may be threadedly fittedin the lower threaded hole 63 a of the lower body section 63 by means ofa suitable tool such as a wrench or the like fitted on the tighteningoperation portion 65 d of the lower projection section 65. The ballmember holding portion 65 e is formed with a recess 65 f of ahemispherical shape which is downwardly open. The recess 65 f has theball member 65 b supported therein in a rollable manner or rollably andin such a manner that the ball member 65 b is externally exposed at apart thereof. The lower projection section 65 is so arranged that theball member 65 b may be abutted against the inner peripheral surface ofthe pipe material P. A position of the ball member 65 b of the lowerprojection section 65 with respect to the lower body section 63 may besuitably varied by adjusting a degree at which the threaded portion 65 cof the lower projection section 65 is fitted in the lower threaded hole63 a of the lower body section 63. In the illustrated embodiment, aposition at which the abutment portion 59 b of the upper projectionsection 59 and the ball member 65 b of the lower projection section 65each are abutted against the inner peripheral surface of the pipematerial P is set so as to restrain a variation in distance between thetorch head 3 and the inner peripheral surface of the pipe material P.The above-described arrangement of the gap formation spacer member 7 inthe illustrated embodiment restrains a reduction in distance between theopening 33 a of the convergent nozzle 33 of the torch head 3 and theinner peripheral surface of the pipe material P due to a weight of thetorch head 3 and/or deflection of the torch body 5, to thereby ensurethat a padding W of a uniform size may be formed on the inner peripheralsurface of the pipe material P.

[0058] The deflection restraint spacer member 9 is made of brass and, asshown in FIGS. 1 and 12 to 14, includes an upper body support half 69, alower body support half 71 and an abutment member 73 which are combinedwith each other to circumferentially surround the torch body 5. FIGS. 12and 13 are a side elevation view of the gap formation spacer member 7and a bottom view thereof, respectively, and FIG. 14 is a sectional viewtaken along line XIV-XIV of FIG. 12. The upper body support half 69 isformed into a semi-circular shape in section so as to circumferentiallysurround an upper portion of the torch body 5 and includes four bolthead arrangement grooves 69 a and four bolt insertion through-holes 69b. The bolt insertion through-holes 69 b each are formed so as tocommunicate with each of the bolt head arrangement grooves 69 a and thelower body support half 71.

[0059] The lower body support half 71 is formed into a semi-circularshape in section so as to circumferentially surround a lower portion ofthe torch body 5 and includes a groove 71 a, two lower threaded holes 71b and four upper threaded holes 71 c. The groove 71 a is formed so as toextend in a direction in which the torch body 5 extends and bedownwardly open. The lower threaded holes 71 b each are formed throughthe lower body support half 71 so as to communicate with a bottom of thegroove 71 a. The upper threaded holes 71 c each are arranged so as tocommunicate with the upper body support half 69 in a manner to bealigned with each of the bolt insertion through-holes 69 b of the upperbody support half 69. The lower body support half 71 is fixed to theupper body support half 69 by means of four bolts 75 threadedly fittedin the upper threaded holes 71 c through the bolt insertionthrough-holes 69 b, respectively. The abutment member 73 is formed intoa substantially semi-circular plate-like shape and so as to extend in alongitudinal direction of the pipe material P. Also, the abutment member73 is arranged so as to vertically downwardly project from the lowerbody support half 71, to thereby be abutted against the inner peripheralsurface of the pipe material P while being fitted in the groove 71 a ofthe lower body support half 71. Further, the abutment member 73 includestwo bolt head arrangement grooves 73 a which are formed so as to bedownwardly open and two bolt insertion through-holes 73 b. The boltinsertion through-holes 73 b are arranged so as to communicate with thebolt head arrangement grooves 73 a. Also, they communicate with thelower body support half 71 while being aligned with the lower threadedholes 71 b of the lower body support half 71. The abutment member 73 isfixed to the lower body support half 71 by means of two bolts 77threadedly fitted in the lower threaded holes 71 b through the boltinsertion through-holes 73 b, respectively. The above-describedarrangement of the deflection restraint spacer member 9 in theillustrated embodiment effectively prevents the torch body 5 fromleaping or jumping in the pipe material P during buildup welding.

[0060] Referring now to FIGS. 15 to 17, another embodiment of a torchfor powder plasma buildup welding according to the present invention isillustrated, wherein FIG. 15 is a plan view showing a peripheralstructure of a torch head of a torch of the illustrated embodiment, FIG.16 is a partially broken-away side elevation view of the torch head andFIG. 17 is a bottom view of the torch head. FIG. 16 also shows a pipematerial P′ to be subjected to buildup welding. The torch of theillustrated embodiment is constructed so as to carry out connection andseparation of a torch head with respect to a connection member by meansof bolts inserted therein from a side of the torch head. Also, in thetorch of the illustrated embodiment, an insulation flange constitutes agap formation spacer member. The torch of the illustrated embodimentgenerally designated at reference numeral 101 is essentially constructedin a manner similar to the torch shown in FIGS. 1 and 2. Thus, the torch101 includes a torch head 103 and a torch body 105 for connecting a bodyof a welding machine (not shown) and the torch head 103 to each othertherethrough. In the torch of the illustrated embodiment, the torch head103 and a part of the torch body 105 are inserted into the pipe materialP′. Then, the pipe material P′ is rotated and the torch head 103 ismoved in the pipe material P′, resulting in a padding W′ of a spiralshape being formed on an inner peripheral surface of the pipe materialP′, leading to buildup welding. In the illustrated embodiment, the pipematerial P′ is formed into an inner diameter of 38 mm. The torch body105, as shown in FIG. 16, includes a connection pipe 111 and pipes 113,115, 117 . . . arranged in the connection pipe 111 for feeding of a DCcurrent, gas and the like to the torch head 103. In the illustratedembodiment, the torch body 105 is formed into a length of about 4 m. Thetorch head 103 is connected to the connection pipe 111 through a firstconnection member half 121 and a second connection member half 123cooperating with each other to constitute a connection member 119 andthrough an insulation flange 125. The torch head 103 includes anelectrode support 131, a convergent nozzle 133, a nozzle support 135 forsupporting the convergent nozzle 133 therein and a head-side insulationmember 137. The electrode support 131 is formed therein with a pluralityin-head passages such as an in-head passage 131 b for plasma gas and thelike. The in-head passages are arranged so as to communicate through acommunication hole 121 d of the first connection member half 121 and thelike with the plural pipes in the torch body 105 such as the plasma gaspipe 113 and the like, respectively. Also, a first pipe for feedingcooling water (cooling water feed pipe) which is one of the plural pipesconstitutes a first conductive portion electrically connected to anegative electric pole of a DC power supply of a welding machine. Thispermits a current to be fed to a bar-like electrode in the electrodesupport 131 through the first cooling water feed pipe (the firstconductive portion), the first connection member half 121 and the like.

[0061] The convergent nozzle 133 is formed into a substantiallycylindrical shape of which a diameter is gradually reduced toward adistal end of the bar-like electrode. The convergent nozzle 133 issupported in the nozzle support 135 so as to surround the bar-likeelectrode while being kept spaced from the bar-like electrode at apredetermined interval. Also, the convergent nozzle 133 has a shield cap134 arranged therearound while being threadedly fitted in the nozzlesupport 135.

[0062] The nozzle support 135 is formed therein with a plurality ofin-head passages such as an in-head passage 135 c for feeding shieldgas, an in-head passage 135 f for discharging cooling water, and thelike. The shield gas in-head passage 135 c is arranged so as tocommunicate through a communication hole 123 d of the second connectionmember half 123 to the shield gas pipe 115 of the torch body 105. Thecooling water discharge in-head passage 135 f is arranged so as tocommunicate through the communication hole 123 d of the secondconnection member half 123 with the second cooling water discharge pipe117 of the torch body 105. A second cooling water feed pipe (not shown)which is one of the plural pipes constitutes a second conductive portionelectrically connected to a positive electric pole of the DC powersupply of the welding machine. This permits a current to be fed from thepositive electric pole through the second cooling feed pipe (the secondconductive portion), second connection member half 123, nozzle support135 and the like to the convergent nozzle 133.

[0063] The connection member 119 is constituted by the first connectionmember half 121 and second connection member half 123. The firstconnection member half 121 and second connection member half 123 has agap or cavity formed therebetween, in which a projection portion 137 bof the head-side insulation member 137 is fitted. The first connectionmember half 121 is joined to the electrode support 131 and providedtherein with a plurality of feed holes 121 a and two threaded holes 121b (FIG. 15). The feed holes 121 a and threaded holes 121 b each areformed so as to extend through the first connection member half 121 in athickness direction thereof. The feed holes 121 a each include a fithole 121 c positioned on a side of the torch body 105 and asmall-diameter communication hole 121 d positioned on a side of thetorch head 103 and formed into a diameter smaller than the fit hole 121c. The fit holes 121 c of the first connection member half 121 have theplural pipes of the torch body 105 fitted therein, respectively, and thecommunication holes 121 d are arranged so as to communicate with thepipes 113 . . . , the in-head passage 131 b of the electrode support 131and the like, respectively. The second connection member half 123 isjoined to the nozzle support 135 and includes a plurality of feed holes123 a and two threaded holes 123 b (FIG. 17). The feed holes 123 a andthreaded holes 123 b each are formed so as to extend through the secondconnection member half 123 in a thickness direction thereof. The feedholes 123 a each include a fit hole 123 c positioned on a side of thetorch body 105 and a communication hole 123 d positioned on a side ofthe torch head 103 and formed into a diameter smaller than the fit hole123 c. The fit holes 123 c have the plural pipes 115, 117 . . . of thetorch body 105 fitted therein, respectively, and the communication holes123 d are arranged so as to communicate with the pipes 115, 117 . . . ofthe torch body 105, the in-head passages 135 c, 135 f, and the like,respectively.

[0064] In the powder plasma buildup welding torch of the illustratedembodiment, as shown in FIG. 15, the electrode support 131 of the torchhead 103 is formed with a plane 131 g facing a front of the powderplasma buildup welding-torch (on a left side in FIG. 15) and two boltinsertion through-holes 131 h open to the plane 131 g. The electrodesupport 131 of the torch head 103 is fixed to the first connectionmember half 121 of the connection member 119 by means of bolts 149Ainserted through the bolt insertion through-holes 131 h of the electrodesupport 131 of the torch head 103 and threadedly fitted in the threadedholes 121 b of the first connection member half 121. Also, as shown inFIG. 17, the nozzle support 135 of the torch head 103 is formed with aplane 133 b facing the front of the powder plasma buildup welding torch(on a left side in FIG. 17) and two bolt insertion through-holes 133 copen to the plane 133 b. The nozzle support 135 of the torch head 103 isfixed to the second connection member half 123 by means of bolts 149Binserted through the bolt insertion through-holes 133 c and threadedlyfitted in the threaded holes 123 b of the second connection member half123. Such fixing between the nozzle support 135 and the secondconnection member half 123 cooperates with the above-described fixingbetween the electrode support 131 and the first connection member half121 to carry out fixing between the torch head 103 and the connectionmember 119.

[0065] The insulation flange 125, as shown in FIGS. 15 to 18, is formedinto a cylindrical configuration having a diameter (36 mm) smaller thanthe-above-described inner diameter (38 mm) of the pipe material P′. FIG.18 is a plan view of the insulation flange 125 which is viewed from aside of the torch body 105. The insulation flange 125 is abutted at alower end thereof against the inner peripheral surface of the pipematerial P′. Such arrangement permits the insulation flange 125 to actas a gap formation spacer member. The insulation flange 125 has athrough-hole 125 a formed therein so as to extend through a centralportion thereof, in which the plural pipes 113, 115, 1171 . . . arearranged. The central through-hole 125 a includes a large-diameterportion 125 b and a small-diameter portion 125 c smaller in diameterthan the large-diameter portion 125 b, between which a stepped portion125 d is formed. The large-diameter portion 125 b has the connectionpipe 111 of the torch body 105 fitted therein.

[0066] The insulation flange 125 is formed with three first boltinsertion through-holes 125 e open to the stepped portion 125 d and foursecond bolt insertion through-holes 125 f. The first bolt insertionthrough-holes 125 e, as shown in FIGS. 15 and 17, each include alarge-diameter portion 125 g positioned on a side of the torch head 103and a small-diameter portion 125 h positioned on a side of the torchbody 105. The insulation flange 125 and torch body 105 are fixed to eachother by means of bolts 147A inserted from the first bolt insertionthrough-holes 125 e into the torch body 105 and threadedly fitted inthreaded holes 111 f formed in the torch body 105. More specifically,the bolts 147A each are threadedly fitted in each of the threaded holes111 f while being kept inserted through the small-diameter portion 125 hof the first bolt insertion through-hole 125 e and keeping a head of thebolt arranged in the large-diameter portion 125 g.

[0067] The second bolt insertion through-holes 125 each include alarge-diameter portion 125 i positioned on a side of the torch body 105and a small-diameter portion 125 j positioned on a side of the torchhead 103. The insulation flange 125 and the first connection member half121 of the connection member 119, as shown in FIG. 15, are fixed to eachother by means of bolts 147B inserted through the second bolt insertionthrough-holes 125 f positioned at an upper portion of the insulationflange 125 into the first connection member half 121 and threadedlyfitted in threaded holes 121 e formed in the first connection memberhalf 121, respectively. More specifically, the bolts 147B each arearranged so as to extend through the small-diameter portion 125 j of thesecond bolt insertion through-hole 125 f and threadedly fitted in eachof the threaded holes 121 e of the first connection member half 121while positioning a head thereof in the large-diameter portion 125 i.Also, as shown in FIG. 17, the insulation flange 125 and the secondconnection member half 123 of the connection member 119 are fixed toeach other by means of bolts 147C inserted from the second boltinsertion through-holes 125 f positioned at a lower portion of theinsulation flange 125 into the second connection member half 123 andthreadedly fitted in threaded holes 121 f formed in the secondconnection member half 123. More specifically, the bolts 147C each areinserted through the small-diameter portion 125 j of the second boltinsertion through-hole 125 f and threadedly fitted in each of thethreaded holes 121 f of the second connection member half 123 whilepositioning a head thereof in the large-diameter portion 125 i. Thus,the insulation flange 125 and connection member 119 are fixed to eachother due to such fixing between the insulation flange 125 and the firstconnection member half 121 and that between the insulation flange 125and the second connection member half 123.

[0068] Referring now to FIGS. 19 to 21, a deflection restraint spacermember incorporated in a further embodiment of a torch for powder plasmabuildup welding according to the present invention is illustrated,wherein FIG. 19 is a plan view of the spacer member, FIG. 20 is a sideelevation view thereof and FIG. 21 is s sectional view taken along lineXXI-XXI. The deflection restraint spacer member generally designated atreference numeral 109 includes a first body support half 169 and asecond body support half 171 which are combined with each other tocircumferentially surround a torch body. The deflection restraint spacermember 109 is formed into a cylindrical shape like a straw bag which isexpanded at a central portion thereof. The central expansion thus formedis formed into an outer diameter smaller than an inner diameter of apipe material and an inner diameter which permits the torch body to betightly fitted therein. The first body support half 169 is formed into asemi-circular shape in section so as to circumferentially surround anupper portion of the torch body and provided thereon with four bolt headarrangement grooves 169 a and four bolt insertion through-holes 169 b.The bolt insertion through-holes 169 b are formed so as to be open tothe bolt head arrangement groove 169 a and second body support half 171.

[0069] The second body support half 171 is formed into a semi-circularshape in section so as to circumferentially surround a lower portion ofthe torch body and provided with four threaded holes 171 c. The threadedholes 171 c are arranged so as to be open to the first body support half169 while being respectively aligned with the bolt insertionthrough-holes 169 b of the first body support half 169. The second bodysupport half 171 is fixed to the first body support half 169 by means offour bolts 175 inserted through the bolt insertion through-holes 169 band threadedly fitted in the threaded holes 171 c of the second bodysupport half 171. In the deflection restraint spacer member 109 thusconstructed, the second body support half 171 is abutted at a lower endthereof against an inner peripheral surface of a pipe material, tothereby prevent leaping of the torch body. The gap formation spacermember constituted by the insulation flange 125 shown in FIGS. 15 to 18and the deflection restraint spacer member 109 shown in FIGS. 19 to 21may be suitably used for a powder plasma buildup welding torch whichcarries out buildup welding on an inner peripheral surface of a pipematerial having a relatively small inner diameter (about 40 mm or less).

[0070] As can be seen from the foregoing, the powder plasma buildupwelding torch according to the present invention is so constructed thatthe torch head is detachably or replaceably connected to the torch body.Such construction permits welding to be attained in conformity to anysize of a pipe material to be subjected to welding, any configurationthereof and the like. Thus, the present invention facilitatesapplication of the torch to buildup welding while eliminatingreplacement of the whole powder plasma buildup welding torch required inthe prior art. Also, when any trouble occurs in the torch head, torchhead may be readily repaired because it is detachably mounted on thetorch body.

[0071] Also, arrangement of the gap formation spacer member in the torcheffectively prevents a variation in distance between the opening of theconvergent nozzle of the torch head and an inner peripheral surface of apipe material subjected to welding due to a weight of the torch headand/or deflection of the torch body, to thereby ensure that a padding ofa uniform size is satisfactorily formed on the inner peripheral surface.

[0072] Further, arrangement of the deflection restraint spacer memberprevents leaping of the torch body.

[0073] While preferred embodiments of the invention have been describedwith a certain degree of particularity with reference to the drawings,obvious modifications and variations are possible in light of the aboveteachings. It is therefore to be understood that within the scope of theappended claims, the invention may be practiced other wise than asspecifically described.

What is claimed is:
 1. A torch for powder plasma buildup welding,comprising: a torch head adapted to be inserted into a pipe material ofa continuous length to carry out buildup welding on an inner peripheralsurface of the pipe material; and a torch body formed into a continuouslength and having said torch head mounted on a distal end thereof; saidtorch head being replaceably connected to said torch body.
 2. The torchas defined in claim 1, wherein said torch head includes a convergentnozzle having an opening; and either said torch head or said torch bodyis provided with a gap formation spacer member which is abutted againstthe inner peripheral surface of the pipe material to keep a distancebetween said opening of said convergent nozzle of said torch head andthe inner peripheral surface of the pipe material substantially constantduring welding.